1. The Field of the Invention
The present invention relates to methods for manufacturing semiconductor devices. More particularly, the present invention relates to a method of resist stripping for use during fabrication of semiconductor devices.
2. The Relevant Technology
During the processing of semiconductor wafers used in the manufacture of integrated circuits and other semiconductor devices, it is necessary in various processing steps to etch or strip certain areas of the wafer to remove photoresist coatings applied to the wafer, and to otherwise clean the wafer. The removal of photoresist coatings by a stripping process typically leaves a residue of resist material on the wafer that can be difficult to remove in a subsequent cleaning process.
Conventional processes for cleaning semiconductor wafers include contacting the wafer with a liquid solvent of a desired composition such as an organic solvent. The composition may be stirred or otherwise caused to flow across or against the surfaces of the wafers to provide a washing action. Cleaning of the wafer utilizing such liquid solvents is typically done by dipping the wafer in a bath of the liquid solvent.
Resist materials have been typically removed from wafers in the past by utilizing a variety of liquid chemical compounds and mixtures. There are several drawbacks with the use of liquid stripping compositions to remove photoresist materials. These include not being able to remove deep UV baked, implant-hardened or plasma hardened photoresist. In addition, use of liquid stripping compositions can leave behind traces of resist film on the wafer as well as nondissolved yield limiting contaminants originating from the liquid stripping compositions on the wafer.
A resist stripping method utilizing vaporized stripping compositions is disclosed in U.S. Pat. No. 4,867,799 to Grebinski. The method includes positioning a wafer within a treating chamber with the surface to be treated exposed. Ammonia vapor is contacted with water vapor and/or hydrogen peroxide vapor adjacent to the surface of the wafer to provide a hot mixture comprising at least ammonia and ammonium hydroxide which is impinged on the surface of the wafer. The contacting of the ammonia with water and/or hydrogen peroxide is immediately prior to and/or simultaneous with the impinging step.
Other conventional resist strip technologies typically use large amounts of oxygen (O.sub.2) to perform the stripping step. The addition of water to O.sub.2 to passivate and strip metal etched wafers has also been widely used in the industry.
Other methods of stripping resist coatings utilize O.sub.2 plasmas, or combinations of a plasma step and then a liquid acid dip. For example, a microwave stripper system utilizes microwave induced plasma of atomic oxygen at low pressure to strip photoresist from a wafer. Other components such as water and nitrogen can also be used in the microwave stripper system, in either a single step with oxygen, or in a two-step process including passivation and stripping.
Since resist materials are typically made of hydrocarbon polymers, the oxygen utilized in the above resist stripping techniques reacts with carbon in the polymers to form strong carbon-oxygen bonds. Although the oxygen etches the resist very fast, a residue is left having carbon-oxygen bonds, which is difficult to remove in a subsequent cleaning process. The resist is also dehydrated by reaction with the oxygen, which further hardens the remaining residue.
Accordingly, there is a need for improved methods that overcome or avoid the above problems and difficulties.